1. Field of the Invention
The invention relates to a negative feedback broadband control amplifier of the kind comprising an amplifier (4) whose input is connected to the output of a differential combining circuit (3) and whose output is connected to the signal input (6) of a signal splitter (5) having a factor .alpha., a transfer first output (8) of the signal splitter (5) being coupled to the output terminal (12) of the control amplifier, a second output (7) of the signal splitter (5) being coupled via a network (11) to the output terminal (12) of the control amplifier and also to a subtractive first input (2) of the combining circuit (3), a second input of which is coupled to the input terminal (1) of the control amplifier.
Control amplifiers of this type can be used, for example as input amplifiers in a receiver for use in optical fibre systems, to compensate for the length and temperature dependent attenuation of the optical link.
2. Description of the Related Art
A control amplifier of such a type is disclosed in U.S. Pat. No. 4,219,788. This prior art control amplifier has the disadvantage that the open loop gain depends on the factor .alpha. of the signal splitter. This renders it impossible to produce a broadband control amplifier having a signal splitter in the negative feed back loop and having a wide control range.